Sexual and gender minorities (SGMs) have been documented in every region of the world. In spite of reported abuse, discrimination and stigma, little is known about their mental health (MH). Even less is known about the development of appropriate MH treatment interventions. Evidence-based treatments (EBTs) addressing poor MH are being implemented in low- and middle-income countries (LMICs) using appropriate, affordable and sustainable delivery modalities (e.g. lay providers, mHealth). These advances create opportunities to provide MH care to SGMs not previously possible. To develop and implement EBTs, longitudinal research is necessary to inform us of the unique MH needs, determinants and treatment preferences of this understudied population. Pilot data for this study suggest that: SGMs can be identified and recruited in LMICs across SGM groups; prevalence of depression, anxiety, suicidal ideation, and posttraumatic stress disorder among SGMs is extremely high; and there are variations in MH symptomatology and determinants by SGM group and country. There is an urgent need for longitudinal cohort studies that include SGMs from heterogeneous LMICs to understand the influence of culture and context on MH needs, predictors and EBT preferences, and to develop locally sustainable EBTs and methods for generalizability. Inclusion of methods (i.e. Discrete Choice Experiments) that identify optimal EBT approaches specific to SGM groups, culture and context will accelerate the translation of observational research to EBT implementation and provide a model that can be used to identify appropriate EBTs for SGMs in other diverse contexts and low resource settings. The SGM Mental Health in LMICs (SMILE) study represents paradigm-shifting research by defining SGMs based on gender identity and attraction -inherent biological characteristics- rather than sexual behavior. SMILE study aims are: ? Aim 1: Estimate prevalence of anxiety, depression, PTSD, suicidal ideation and substance abuse symptomatology among 7 SGM groups in 3 culturally diverse LMICs (Brazil, Kenya, Vietnam) ? Aim 2: Identify cultural, contextual, interpersonal and individual determinants of MH over time, by and across SGM group and country. ? Aim 3: Determine SGMs? MH intervention preferences through Discrete Choice Experiments (DCEs). To accomplish these aims we will use a two-pronged recruitment strategy that includes respondent-driven sampling and a mass media campaign to develop a cohort of 10,500 SGM (500 participants from 7 SGM groups in 3 countries). Study participants will complete online surveys at baseline, 12- and 24-months to assess MH symptomology, determinants, and treatment preferences. DCEs will be developed and included in the 24-month survey to elicit preferences for EBTs that are SGM group, culture and context specific. SMILE addresses all three NIMH priorities identified in the Notice of Special Interest in Research on Health of SGM Populations (NOT-MD-19-001) and priorities of two other NIH Program Announcements.